The present invention relates generally to scanning beam devices. More specifically, the present invention relates to scanning fiber devices that have a memory element which includes data that improves operation of the scanning fiber devices.
There is a growing market for micro-optical displays and small image acquisition systems (e.g., cameras). Scanning beam systems fill the need, but the lack of low cost micro-optical systems with a wide field of view (FOV) have been the most significant barrier for reducing the size of scanning beam systems for use in minimally invasive medical imaging (flexible endoscopes), surveillance, industrial inspection and repair, machine and robotic vision systems, and micro-barcode scanners.
Most conventional scanning beam systems use a movable scanning element, such as a rotating or oscillating mirror. Light, such as a laser beam, is projected onto the moving mirror to scan the light across a predetermined linear pattern or two-dimensional pattern (e.g., raster) at a scan frequency that is sufficient for the particular application. The FOV is determined by the scanning amplitude and the particular optical design of the system. While the scanning element may be scanned at any frequency, in most embodiments, a drive signal is chosen to substantially match the resonant frequency of the scanning element. As shown in FIG. 1A, it is often useful to scan the light at a frequency within a “Q-factor” of the resonant frequency of the scanning element. Scanning the light within the Q-factor allows for scanning at desired angles and displacements while using a minimal amount of energy to obtain the desired angles and displacement.
Combining both high resolution (>400,000 pixels) and wide FOV (>30 degrees) in a single display or camera is a difficult technical challenge. There is a tradeoff between optical scanning frequency versus scanning amplitude (FOV) for all mirror-scanning devices. The faster the mirror scans, the greater the forces acting on the mirror, which deforms the mirror surface, degrading image quality. This limitation is especially true for the small, low cost resonant mirror scanners. Rotating polygon mirror scanners can overcome this limitation or tradeoff between scan frequency and amplitude, except they are usually bulky, and costly. In the case of a resonant mirror scanner, the mirror cannot scan more than a few degrees in amplitude at frequencies of 20 kHz to 40 kHz, as required for sVGA raster scanning displays. Since the optical beam reflects from the scanning mirror, the optical FOV is twice the total mirror deflection angle (i.e., the FOV=2 times mirror scan amplitude). However, at sVGA resolution and scan frequencies, optical FOVs on the order of 30 degrees to 60 degrees cannot be achieved using a low cost resonant mirror scanner as the basis for micro displays.
Recently, resonant mirror optical scanning systems have been developed that include silicon micro-machining techniques to make micro-electromechanical systems (or MEMS) devices. In theory, this technique can manufacture durable mirror-based optical scanners at lower costs. Nonetheless, there is still a tradeoff between scan amplitude and scan frequency of the resonant scanning mirror.
To that end, an improved scanning beam system has been developed which involves the use of a cantilevered optical fiber that is scanned in one or two dimensions to project light out of the end of the optical fiber to form an image. In addition to image formation and micro-display applications, image acquisition is also possible with the addition of a sensor, such as a photosensor. To acquire an image, the light projected out the end of the scanning optical fiber is reflected from the target area and the backscattered light is captured and measured with the sensor in time series. Because the motion of the fiber is predictable and repeatable, the reflected light intensity measured at the sensor can be sequentially correlated with the position of the optical fiber, and a two-dimensional image may be created one ‘pixel’ at a time. For ease of reference, the terms “scanning beam system” and “scanning fiber system” will be used generically to encompass systems that are used for image display and/or image acquisition.
In comparison to traditional scanning beam devices, scanning fiber technology offers many advantages. The small mass of the optical fiber scanner allows high scan angles at video rates—typically between about 1 kHz and about 50 kHz, and preferably between about 5 kHz and about 25 kHz. Optical fiber scanners also have a smaller ‘footprint’, taking up less space and can be conveniently packaged into a small (<1 mm) diameter cylindrical endoscope or catheter housing.
When used for image acquisition, the fiber scanner has numerous applications in the areas of medical endoscopy and other remote imaging methods, where the millimeter package diameter size allows exploration into areas previously untouched by traditional methods. Commonly owned U.S. Pat. Nos. 6,563,105 B2 and 6,294,775 B1 and U.S. Patent Application Publication Nos. 2001/0055462 A1, and 2002/0064341 A1 (all to Seibel) describe some useful image acquisition systems, the complete disclosures of which are incorporated herein by reference.
It is contemplated that commercial scanning beam systems of the present invention will comprise a base station and a scanning beam device. One particular use of the systems of the present invention is for minimally invasive medical procedures in which the scanning beam device is in the form of a flexible endoscope that may be used to image an interior of a body lumen, body cavity, and/or hollow organ. As can be appreciated, for different body lumens or for different imaging procedures, it may be desirable to use different devices that have different properties, such as different sizes, fields-of-view, resolutions, color capability, or the like. However, the differences in characteristics for each of the devices will generally require a different control routine to properly operate the device and to be able to take advantage of the capabilities of the device. In particular, the devices will often have different resonant frequencies, and the base station will need to alter a drive signal to match the resonant frequency of the specific fiber.
Importantly, even if two of the same model scanning beam devices are used with the base station, because of manufacturing tolerances, oftentimes the two same model devices will still have differences in their resonant frequencies or other parameters that will affect the operation of the device. Consequently, in order to be able to use a single base station with the different scanning beam devices, it may be necessary to determine the operating parameters for each and every device prior to use so that the base station can reconfigure its control routine to match the parameters of the device. Without such parametric data, the base station may not be able to properly operate the different of scanning beam devices. While it is may be possible to determine the parameters of each device, such calibration is time consuming and lengthens the setup procedure. In some cases, it may not even be possible to determine all of the relevant parameters of the device. As different models of devices are developed for use with the base stations, in which each of the devices will have different characteristics than other models, the time involved in reconfiguring the base station to allow the base station to take advantage of the different capabilities of the devices will increase and will add significantly to the time of the scanning procedure.
In light of the above, it would be desirable to provide improved base stations, devices, systems, and methods. It would be further desirable to provide universal base stations that have a reduced set up time and reduced number of calculations associated with reconfiguring a base station for use with different devices. It would be especially desirable if the enhanced and rapid configuration methods resulted in improved safety to the patient and reliability of image construction.